1. Field of the Invention
The present invention is directed to a method and apparatus for the quantitative determination of particles in fluids. The preferred embodiments will find use for quantitative analysis of fat in milk and other dairy fluids.
2. Description of the Prior Art
The present invention is directed to the field of quantitative determination of particles in fluids. The term particle shall be used in its broadest sense and shall typically not only be restricted to mean pieces of solid matter in another phase, but also include the situation of small volumes of liquid in another liquid phase--an example would be micelles or small globules dispersed in a bulk liquid phase such as in an emulsion, or fat globules in a liquid such as milk.
In addition, the term `fluid` shall also be taken to include the gaseous phase though it is envisaged that most embodiments will be used in applications where the fluid is a liquid.
Most apparatus which is currently used for the quantitative determination of particles in a fluid are relatively complex in nature. Their degree of complexity is at least partially a cause for several disadvantages:
they are relatively expensive; PA1 they are often relatively delicate and generally unsuitable for use in the field or in normal manufacturing and processing environments; PA1 they are generally specific in purpose and often cannot be readily adapted for other applications; PA1 they are often unable to be used for monitoring an in-line sample arrangement--most embodiments require samples to be removed from the production line and placed in the apparatus for analysis. PA1 an emitter set comprising one or more light emitters in turn providing one or more sample light signals; PA1 a detector set comprising one or more light detectors sensitive to the output of the light emitters, PA1 the detector providing output values which can be evaluated by processing means for providing a value indicative of the fluid particle content. PA1 influencing either or both the voltage and current of at least one light emitter to maintain light output at a predetermined level; PA1 influencing the sensitivity of at least one light detector to match the light output of at least one light emitter, and PA1 providing a signal available to processing means for use in correction when providing a value indicative of particle content. PA1 their path length through the fluid sample being analysed, and PA1 their relative path angle through the fluid sample being analysed. PA1 their path length through the fluid sample being analysed; PA1 their relative path angle through the fluid sample being analysed; PA1 the output intensity of the emitter producing said signal; PA1 the proportion of transmitted to reflected or scattered light, and PA1 wavelength. PA1 milk and other dairy based fluids; PA1 substances containing fluidised fat particles, globules, and suspensions; PA1 blood, plasma, semen, urine and other biological fluids; PA1 oils and lubricants, and PA1 inks, paints, and liquid pigments. PA1 their path length through the fluid sample being analysed; PA1 their relative path angle through the fluid sample being analysed, PA1 whether the emitted light beam is directly incident upon the detector. PA1 where a plurality of emitters concurrently work and act in conjunction with a plurality of light detectors on a one to one basis, and where each signal path is substantially identical in characteristics so that a range of supposedly identical readings are simultaneously obtained for averaging or other comparison; PA1 the situation where a single emitter acts with several detectors concurrently on a one to many basis, and where the physical signal path characteristics (e.g. path lengths, angles etc.) are substantially identical so that the values obtained may be averaged or otherwise compared; PA1 the situation of the preceding paragraph wherein the characteristics of the signal paths from the emitter to each detector differs so that a range of different signal path values may be obtained for subsequent evaluation; PA1 where a single light detector may concurrently receive light from a plurality of light emitters, the signal path from each light emitter to the single light detector being substantially identical so the values may be averaged or otherwise compared; PA1 the situation of the preceding paragraph in which each emitter to detector signal path differs.
Much of the art relies on spectroscopic techniques for quantitative determination of particle presence in a fluid. Most of these techniques are based on infrared spectroscopy and are only useful in many cases for detecting and quantitatively determining organic or organometallic particles in the fluid. An example is the subject matter of NZ Patent No. 192325 which describes a method of quantitative measurement of fat in a sample by using an infrared absorption technique and evaluating the infrared absorption characteristic of saturated carbon-hydrogen bond stretching. However this and corresponding methods are generally specific to the quantitative analysis of particular categories of compounds and could be influenced by the presence of substances other than those of interest which are also present in the sample.
International Patent Appln No. WO 92/17767 is directed to a similar method of quantitative fat determination in an emulsion and also takes into account infrared absorption peaks due to other (than C--H bond excitation) as well. While this technique would also appear to improve selectivity (and thus have the potential to eliminate interference from other substances present in the sample) it also claimed that more accurate determinations can be carried out directly from full milk, without a preceding homogenisation treatment. However the invention described in this specification also possesses many of the general disadvantages described above.
French Patent No. FR 2050525 describes a method where an infrared beam is reflected off parallel transparent walls bounded on the outside by the sample fluid. Here only part of the beam will be reflected (and some absorbed or transmitted through the sample liquid) to be measured as it exits the chamber. The intensity of the reflected beams reflects particle content, supposedly. However this method will have limitations in the number and type of different fluids with which it may be used.
Russian Patents Nos. SU 983538 and SU 1748058 are also directed to methods of particle determination in fluids though rely upon the use of expensive or complex equipment; one of which prefers the use of a maser which is not an off-the-shelf item in most countries.
In general the bulk of the prior art does not allow for the continuous or in-line monitoring of sample fluid and are generally and relatively inflexible in how they may be used or applied.
It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.